linux-kernel - Re: [PATCH 07/12] time: Try to catch clocksource delta underflows

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Message-ID: <20150307093435.GF30888@gmail.com>
Date:	Sat, 7 Mar 2015 10:34:35 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	John Stultz <john.stultz@...aro.org>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Dave Jones <davej@...emonkey.org.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Richard Cochran <richardcochran@...il.com>,
	Prarit Bhargava <prarit@...hat.com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH 07/12] time: Try to catch clocksource delta underflows


* John Stultz <john.stultz@...aro.org> wrote:

> In the case where there is a broken clocksource
> where there are multiple actual clocks that
> aren't perfectly aligned, we may see small "negative"
> deltas when we subtract now from cycle_last.

So this is a typical example where putting argument references is 
really helpful. Consider these two variants:

   deltas when we subtract now from cycle_last.

   deltas when we subtract 'now' from 'cycle_last'.

I had to read the first variant three times until I realized that 
'now' is a C variable misleadingly inserted into English text.

> The values are actually negative with respect to the
> clocksource mask value, not necessarily negative
> if cast to a s64, but we can check by checking the
> delta see if it is a small (relative to the mask)
> negative value (again negative relative to the mask).

typo.

Thanks,

	Ingo
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